1. Technical Field
The present invention relates generally to data communications and more particularly to high-speed wired data communications.
2. Related Art
As is known, communication technologies that link electronic devices are many and varied, servicing communications via both physical media and wirelessly. Some communication technologies interface a pair of devices, other communication technologies interface small groups of devices, and still other communication technologies interface large groups of devices.
Examples of communication technologies that couple small groups of devices include buses within digital computers, for example, PCI (Peripheral Component Interface) bus, ISA (Industry Standard Architecture) bus, an USB (Universal Serial Bus), SPI (System Packet Interface, such as SPI-4) among others.
One relatively new communication technology used in coupling relatively small groups of devices is the HyperTransport (HT) technology, previously known as the Lightning Data Transport (LDT) technology (HyperTransport I/O Link Specification “HT Standard”). The HT Standard sets forth definitions for a high-speed, low-latency protocol that can interface with today's buses like AGP, PCI, SPI, 1394, USB 2.0, and 1 Gbit Ethernet as well as next generation buses including AGP 8x, Infiniband, PCI-X, PCI 3.0, and 10 Gbit Ethernet. HT interconnects provide high-speed data links between coupled devices. Most HT enabled devices include at least a pair of HT ports so that HT enabled devices may be daisy-chained. In an HT chain or fabric, each coupled device may communicate with each other coupled device using appropriate addressing and control. Examples of devices that may be HT chained include packet data routers, server computers, data storage devices, and other computer peripheral devices, among others.
Many communication devices often require significant processing capabilities and significant memory capacity. These communication devices therefore may employ one or more integrated circuits having multiple processors, memory, a processor bus, and interface ports formed therein. An integrated circuit of this type is often referred to as a “System On a Chip” (SOC). Network switches, web servers, and other high capacity devices often require more processing and storage capacity than can be provided by a single SOC. Thus, these devices often include a plurality of SOCs mounted upon a single Printed Circuit Board (PCB) and/or include multiple PCBs each having mounted thereon one or more SOCs. In these instances, the PCBs may be rack mounted and may intercouple via a back plane of the rack. The SOCs on the PCBs couple via traces formed on the PCBs.
Because of the high data rates that it supports, the HT Standard is popular for coupling devices, such as SOCs. The HT Standard, however, has very tight skew requirements. Coupling HT enabled devices via a backplane connection or even via long traces on a Printed Circuit Board, i.e., low quality connections, would violate the HT Standard in many operations. Thus, relatively lower data rate interfaces, e.g., SPI-4, are typically employed across the back plane and/or across long traces.
Therefore, a need exists for methods and/or apparatuses for interfacing devices using the high speed HT interface standard via relatively low quality connections.